JP6831964B2 - Solar cell - Google Patents

Description

Embodiments of the subject matter described herein relate broadly to solar cells. More specifically, embodiments of the subject relate to the manufacturing process and structure of solar cells.

Solar cells are well-known devices for converting solar radiation into electrical energy. A solar cell has a front side facing the sun during normal operation to collect solar radiation and a back side opposite to the front side. The solar radiation that hits the solar cells creates an electric charge that can be used to power external electrical circuits such as loads.

The manufacturing process of a solar cell usually involves a number of steps, including masking, etching, growing, diffusing and other steps. Embodiments of the present invention provide an advantageous solar cell process.

One embodiment relates to a method of manufacturing a solar cell. The silicon thin film is cleaved from the silicon substrate. The back side of the silicon thin film contains a P-type doping region and an N-type doping region. A metal foil is attached to the back side of the silicon thin film. The metal leaf may be advantageously used as an embedded carrier for treating the silicon thin film during the treatment of the front side of the silicon thin film.

Another embodiment relates to a solar cell comprising a silicon thin film having a P-type doped region and an N-type doped region on the back side. The metal foil is adhered to the back side of the thin film to form contacts between the metal foil and the dope region.

Another embodiment relates to a method of manufacturing a solar cell, which comprises a step of adhering a metal leaf to the back side of a silicon substrate. The silicon thin film may then be separated from the back side of the silicon substrate. The metal leaf is used as an embedded carrier for treating the silicon thin film during the treatment of the front side of the silicon thin film.

These and other embodiments, aspects and features of the present invention will be readily apparent to those skilled in the art by reading the entire disclosure, including the accompanying drawings and claims.

A more complete understanding of the subject can be obtained by considering and referring to the embodiments for carrying out the invention and the scope of claims in combination with the following drawings. Similar reference numbers point to similar elements throughout the drawings. Multiple drawings are not drawn at a uniform magnification.

It is sectional drawing which schematically illustrates the manufacture of the solar cell by embodiment of this invention. It is sectional drawing which schematically illustrates the manufacture of the solar cell by embodiment of this invention. It is sectional drawing which schematically illustrates the manufacture of the solar cell by embodiment of this invention. It is sectional drawing which schematically illustrates the manufacture of the solar cell by embodiment of this invention. It is sectional drawing which schematically illustrates the manufacture of the solar cell by embodiment of this invention. It is sectional drawing which schematically illustrates the manufacture of the solar cell by embodiment of this invention.

It is a flow chart of the manufacturing method of the solar cell by embodiment of this invention.

It is a flow chart of the manufacturing method of the solar cell by the alternative embodiment of this invention.

It is sectional drawing of the manufactured solar cell manufactured by the method of FIG.

It is a top view of the metal foil covering the back side of the silicon thin film according to the embodiment of this invention.

It is a flow chart of the manufacturing method of the thin silicon solar cell according to another embodiment of this invention.

The present disclosure provides a number of specific details, including examples of devices, structures, materials and methods, to provide a full understanding of embodiments of the present invention. However, those skilled in the art will appreciate that the present invention can be practiced in the absence of one or more of these specific details. In other cases, well known details are not illustrated or described to avoid obscuring aspects of the invention.

The present disclosure provides techniques for forming thin silicon solar cells using metal foil. Advantageously, the metal leaf may be used during the processing of the front side of the thin film as an embedded carrier for processing the otherwise fragile silicon thin film. Subsequently, the metal leaf may be reused to form a plurality of metal fingers and contacts to the P- and N-emitters on the backside of the thin film.

1 to 6 are cross-sectional views schematically illustrating the manufacture of a thin silicon solar cell according to an embodiment of the present invention. What is shown in FIG. 1 is a silicon substrate 102 on which a P-type dope (P +) region 104 and an N-type dope (N +) region 106 are formed, and these regions are formed on the back side of the substrate 102. Has been done. The P + and N + doped regions may be referred to as P-type emitters and N-type emitters in the context of manufactured solar cells. In the back electrode type solar cell shown in FIG. 1, a plurality of emitters and a plurality of corresponding contacts are provided on the back side of the solar cell. The doped region may be formed, for example, by diffusing the dopant from the dopant source.

The thin dielectric layer 108 may be formed on the backside P + and N + regions for electrical insulation, passivation and / or other purposes. The dielectric layer 108 may contain, for example, silicon oxide and / or silicon nitride. Alternatively, the surface of the emitter may be passivated by means other than forming the dielectric layer 108, such as chemical passivation.

The structure of the solar cell of FIG. 1 may be arranged in an ion implanter, also referred to as an "ion implanter". The ion implanter may be used to implant ions at a predetermined implantation depth 202, as shown in FIG. The ion may be a hydrogen ion (ie, a proton). In alternative embodiments, other ions may be injected or may be injected with hydrogen. For example, helium ions may be injected instead of hydrogen ions or may be injected with hydrogen ions. A planar thin film of silicon above the injection depth may be separated or stripped from the remaining silicon substrate below the injection depth, as the injection volume causes defects at the injection depth. The injection energy controls the injection depth and the thickness of the thin silicon substrate after peeling. For example, the injection energy may be calibrated to cleave a thin film with a thickness in the range of 10 micrometers to 100 micrometers. The peeling may be realized by heating the substrate at a high temperature.

As shown in FIG. 3, the metal foil 306 may be adhered to the dielectric layer 108 on the back side of the silicon thin film 302. The metal foil 306 may be an aluminum foil. In order to facilitate the use of the foil as a carrier of the thin film, the extended region (processed region) of the metal foil 306 may be extended beyond the outer edge of the silicon thin film 302. In an exemplary implementation, the composition of the metal leaf 306 may be Al-1% Si (99% aluminum and 1% silicon) or more generally Al-x% Si, where x% is 0%. ~ 3%. Other compositions of aluminum foil may be used. A metal leaf other than aluminum, such as silver leaf, can also be used.

In one embodiment, an adhesive layer 304 may be used to bond the metal leaf 306 to the back side of the silicon thin film 302. The adhesive layer 304 may be a thin layer of epoxy, silicone, ethylene vinyl acetate (EVA) or other encapsulating material applied to the back side of the substrate. In one implementation, the adhesive layer may be a coating pre-applied to the metal leaf prior to bonding.

In an alternative embodiment, the metal foil 306 may be adhered to the back side of the substrate using an array of contact points between the metal foil 306 and the back side of the substrate. The contact points may be formed by, for example, point melting of the metal leaf using a pulsed laser. In this embodiment, the adhesive layer 304 is unnecessary. The air gap under the foil between the contact points may be removed by flattening the foil.

As shown in FIG. 4, when the foil is used as an integrated or integrated carrier to support the thin film, the front surface 402 of the thin film 302 may be textured and passivated. Surface texture processing works to increase the ability of the silicon surface to absorb light, and surface passivation works to reduce charge recombination on the surface. Surface texturing may be achieved using, for example, a wet surface etching process. Surface passivation may be achieved by chemical passivation or other means.

After that, the glass encapsulation process may be carried out on the front side of the silicon thin film 302. FIG. 5 shows the resulting glass layer 502 attached to the front side using encapsulation material 503.

As shown in FIG. 6, a further step may then be performed on the back side of the silicon thin film 302. These steps include forming metal contacts 604 and 606 in the contact hole for electrical connection to the corresponding P + region 104 and N + region 106, respectively. The first set of the metal contacts 604 may be formed from the metal foil 304 to the P + region 104, and the second set of the metal contacts 606 may be formed from the metal foil 304 to the N + region 106. In one embodiment, metal contacts 604 and 606 may be formed using a laser-based contact forming process. In such a process, the laser scanner may controlally scan the pulsed laser beam over the entire backside of the manufactured solar cell. The pulsed laser beam may form a plurality of contact openings penetrating the adhesive layer 304 and the dielectric layer 108, and the plurality of contact openings may be filled with a metal melted from the foil 306.

Further, a pattern of finger separation 608 may be formed on the foil area in order to electrically separate the first set of metal contacts 604 from the second set of metal contacts 606. The finger separation 608 may be configured such that the fingers of the foil leading to the plurality of contacts fit together.

FIG. 7 is a flow chart of an exemplary method 700 for manufacturing a thin silicon solar cell according to an embodiment of the present invention. In the exemplary method 700 of FIG. 7, a plurality of emitter regions may first be formed on the silicon wafer in the block 702. Silicon wafers may have a thickness greater than or equal to several hundred micrometers and may be referred to as thick handle wafers. The plurality of emitter regions include both a P-doped region and an N-doped region, and may be formed on the back side of the wafer as shown in FIG.

At block 704, a thin silicon thin film may be cleaved from the silicon wafer. For example, the silicon thin film may have a thickness of 10 micrometers to 100 micrometers. In one implementation, cleavage using ion implantation and delamination may be performed as described above in connection with FIG. Alternatively, cleavage may be performed by stripping or etching the sacrificial layer from the front side of the wafer.

In block 706, the metal leaf may be adhered to the silicon thin film as described above in connection with FIG. Specifically, the metal foil may be adhered to the back surface of the silicon thin film. The metal leaf may be 50 micrometers to 1 millimeter thick to provide mechanical support for the thin silicon thin film. In order to facilitate the use of the foil as a carrier of the thin film, the extended region (processed region) of the metal foil may be extended beyond the outer edge of the silicon thin film. In one implementation, adhesion may be achieved by using a laser to heat multiple contacts between the metal foil and the silicon thin film. In another implementation, adhesion may be achieved using a thin adhesive layer coated on the metal leaf.

In the block 708, the metal leaf may be used as an integral carrier for treating the silicon thin film so that the front surface of the silicon thin film can be treated. Treatment of the front surface may include texturing and passivation, as described above in connection with FIG. Surface texture processing and passivation may be achieved, for example, by immersing the thin film in a chemical solution to etch and passivate the front surface. Subsequently, the front side of the metal leaf-assisted silicon thin film may be treated using the glass lamination method, as described above in connection with FIG. Following the processing on the front side, the extended area (processing area) of the metal leaf may be trimmed.

In block 710, a plurality of contacts may be formed from the metal leaf to a plurality of emitter regions. As described above in connection with FIG. 6, the plurality of contacts formed are the first set of contacts 604 for the plurality of P-doped emitter regions 104 and the second set of contacts 606 for the plurality of N-doped emitter regions 106. It may include a set. Further, in order to electrically separate the first set and the second set of contacts, a pattern of finger separation 608 may be formed on the foil.

In an alternative embodiment, the metal leaf is made of a silicon thin film, instead of a step of adhering a continuous metal leaf layer to the back side, followed by a step of creating a finger separation pattern while the foil is attached to the back side. A finger separation pattern may be preformed in the metal leaf before being applied to the back side. FIG. 8 is a flow chart of an alternative method 800 for manufacturing a thin silicon solar cell using such a pre-patterned metal leaf according to an embodiment of the present invention.

As shown in FIG. 8, after the thin silicon thin film is cleaved from the wafer at the block 704, in 806, a pre-patterned metal leaf may be sandwiched between the back side of the silicon thin film and the secondary substrate. The pattern forming of the metal leaf realizes finger separation between the P-type contact and the N-type contact. The sub-board may be transparent so that the laser beam can be transmitted through it. The sub-board may be, for example, a rigid polymer layer such as a polyethylene terephthalate (PET) layer or a fluoropolymer layer. After that, in the block 807, a plurality of contacts may be formed between the metal foil and the plurality of emitter regions. The formation of multiple contacts uses, for example, a pulsed laser transmitted through a secondary substrate to create multiple contact openings and allow metal melted from multiple contact foils to flow into those multiple openings. It may be realized by Then, in block 708, the front surface may be treated as described above in connection with FIG. Following the processing on the front side, the extended area (processing area) of the metal leaf may be trimmed.

FIG. 9 is a cross-sectional view of a manufactured thin silicon solar cell manufactured by the method 800 of FIG. As shown in FIG. 9, the metal leaf 306 provided with the pre-patterned finger separation 908 is sandwiched between the sub-board 902 and the back side of the silicon thin film 302. Further, a P-type contact 904 and an N-type contact 906 are shown. As mentioned above, these contacts may be formed by transmitting a pulsed laser through a transmissive sub-board 902.

FIG. 10 is a plan view of a metal foil covering the back side of the silicon thin film according to the embodiment of the present invention. The figure of FIG. 10 shows a foil portion 1004 that covers the back side of the thin film and an extended region 1006 of the foil that extends beyond the outer edge portion 1002 of the thin film. It should be noted that the extension region 1006 may extend beyond one or more sides of the outer edge and need not extend beyond all sides of the outer edge.

FIG. 11 is a flow chart of a method 1100 for manufacturing a thin silicon solar cell according to another embodiment of the present invention. In the exemplary method 1100 of FIG. 11, at block 1102, a sacrificial layer may be formed on a silicon substrate.

The sacrificial layer may be composed of porous silicon, such as those formed in a biased HF solution. Alternatively, the sacrificial layer may be, for example, silicon with germanium doping and / or carbon doping, both of which can be formed by an epitaxial growth or chemical vapor deposition (CVD) process. The sacrificial layer may be as thin as about 700 micrometers, but may be slightly or significantly thicker, as desired in certain embodiments to perform the functions described herein. It may be thin. For example, in some embodiments, the sacrificial layer may be as thin as 10 micrometers. In some cases, thinner thicknesses may also be used.

Then, in block 1104, an epitaxial layer of silicon may grow on the sacrificial layer. In block 1106, a plurality of emitter regions may be formed in the epitaxial layer, and in block 1108, a dielectric layer may be formed on the plurality of emitter regions.

Then, in block 1110, the metal leaf may be adhered on the plurality of emitter regions. Subsequently, at block 1112, epitaxial lift-off may be performed by selective wet etching or otherwise sacrificial layer removal. After lift-off, the epitaxial layer becomes a silicon thin film of the solar cell. The cross-sectional view of the structure at this point in the process corresponds to the view shown in FIG. As disclosed herein, metal leafs provide structural support and integrated carrier functionality to silicon thin films.

Subsequently, in block 708, the front surface may be treated. After that, in the block 710, a plurality of contacts may be formed between the metal foil and the plurality of emitter regions. That is, after the epitaxial lift-off at block 1110, the process may be continued as described above in connection with FIGS. 4-6.

So far, we have disclosed techniques for forming thin silicon solar cells using metal foil. Advantageously, the metal leaf may be used during the processing of the front side of the thin film as an embedded carrier for processing the otherwise fragile silicon thin film. Subsequently, the metal leaf may be reused to form the contacts of the P-emitter and the contacts of the N-emitter and the metal fingers on the back side of the thin film.

Although specific embodiments of the present invention have been provided, it will be appreciated that these embodiments are for illustration purposes only and are not limiting. Many further embodiments will be apparent to those skilled in the art reading this disclosure.
[Item 1]
A method of manufacturing solar cells
A step of cleaving the silicon thin film from a silicon substrate, wherein the back side of the silicon thin film contains a P-type doped region and an N-type doped region.
A method comprising a step of attaching a metal foil to the back side of the silicon thin film.
[Item 2]
The extended region of the metal leaf extends beyond the outer edge of the silicon thin film.
The method according to item 1, further comprising a step of using the metal leaf as an integrated carrier for treating the silicon thin film.
[Item 3]
A step of forming a first set of contacts between the metal foil and the P-type doped region.
A step of forming a second set of contacts between the metal foil and the N-type doped region.
The method according to item 1, further comprising.
[Item 4]
The method of item 3, wherein the plurality of contacts are formed using a pulsed laser beam.
[Item 5]
The method according to item 1, further comprising a step of forming a finger separation pattern in the metal foil.
[Item 6]
The method of item 5, wherein the finger separation pattern is preformed in the metal leaf prior to attachment to the back side.
[Item 7]
A step of attaching the metal foil to the sub-board before the attachment to the back side is further provided.
The method according to item 6, wherein the sub-board is transparent to a laser beam.
[Item 8]
The method of item 1, wherein the metal leaf is attached to the back side using an adhesive layer.
[Item 9]
The method of item 1, wherein the metal foil is attached to the back side in an array of contact points between the metal foil and the back side of the silicon substrate.
[Item 9]
8. The method of item 8, wherein the contact points are formed by point melting of the metal leaf.
[Item 10]
The method according to item 1, wherein the metal foil contains aluminum.
[Item 11]
A step of texture processing and passivating the front side of the silicon thin film while using the metal foil as a carrier for treating the silicon thin film.
The step of encapsulating the front side of the silicon thin film and
The method according to item 1, further comprising.
[Item 12]
Silicon thin film and
The P-type and N-type doped regions on the back side of the silicon thin film,
The metal foil adhered to the back side of the silicon thin film and
A first set of contacts between the metal foil and the P-type doped region,
A second set of contacts between the metal foil and the N-type doped region,
With a solar cell.
[Item 13]
The solar cell according to item 12, wherein the silicon thin film has a thickness in the range of 10 to 100 micrometers.
[Item 14]
An adhesive layer is further provided between the metal foil on the back side of the silicon thin film and the P-type doped region and the N-type doped region, and the plurality of contacts pass through a plurality of openings in the adhesive layer. Item 12. The solar cell according to item 12.
[Item 15]
The solar cell according to item 12, further comprising a plurality of contact points between the metal foil on the back side of the silicon thin film and the P-type doped region and the N-type doped region.
[Item 16]
The textured and passivated surface on the front side of the silicon thin film and
A glass layer covering the front side of the silicon thin film and
The encapsulating material between the front side of the silicon thin film and the glass layer,
The solar cell according to item 12, further comprising.
[Item 17]
The solar cell according to item 12, wherein the metal foil contains aluminum.
[Item 18]
The solar cell according to item 17, wherein the metal foil contains Al-x% Si, where x% is in the range of 0 percent to 3 percent.
[Item 19]
A step of adhering a metal foil to the back side of the silicon substrate, wherein the back side of the silicon substrate contains a P-type doping region and an N-type doping region.
A step of separating the silicon thin film from the back side of the silicon substrate, and
A step of using the metal leaf as an embedded carrier for treating the silicon thin film during the treatment of the front side of the silicon thin film, and
A method of manufacturing a solar cell.
[Item 20]
19. The method of item 19, wherein the step of separating the silicon thin film is performed by epitaxial lift-off.
[Item 21]
A step of forming a first set of contacts between the metal foil and the P-type doped region.
A step of forming a second set of contacts between the metal foil and the N-type doped region.
A step of forming a plurality of separations between the first set of metal contacts and the second set of metal contacts.
The method according to item 19, further comprising.

Claims (10)

A substrate having a front side facing the sun during normal operation and a back side opposite to the front side.
The P-type and N-type doped regions on the back side of the substrate,
With the P-type doped region and the first dielectric on the N-type doped region,
A first contact that is electrically connected to the P-type dope region through the first dielectric and a second contact that is electrically connected to the N-type dope region through the first dielectric. The metal foil is a metal foil having the contact points of the above, and the metal foil is adhered to the back side of the substrate by an array of contact points between the metal foil and the back side of the substrate, and the contact points are the contact points. With metal foil, including the molten metal part of the metal foil
With
A portion of the metal foil extends beyond the outer edge of the substrate.
Solar cell. An adhesive layer is further provided between the metal foil and the first dielectric, and the metal foil is adhered to the back side of the substrate by a contact opening penetrating the adhesive layer. Item 1. The solar cell according to item 1. The solar cell according to claim 2, wherein the adhesive layer contains a material selected from the group consisting of epoxy, silicon, and ethylene vinyl acetate. The encapsulating material on the front side of the substrate and
With the transparent layer on the encapsulation material
The solar cell according to any one of claims 1 to 3, further comprising. The solar cell according to claim 4, wherein the transparent layer contains glass. The solar cell according to any one of claims 1 to 5, wherein the front side of the substrate is textured. The solar cell according to any one of claims 1 to 6, wherein the substrate contains silicon. The solar cell according to any one of claims 1 to 7, wherein the metal foil contains aluminum. The solar cell according to any one of claims 1 to 8, wherein the metal foil contains Al-x% Si, and x% is in the range of 0% to 3%. A claim that further comprises a finger separation pattern between the first contact and the second contact, the finger separation pattern electrically separating the first contact from the second contact. The solar cell according to any one of 1 to 9.

Images